An orthosis is an external insert, device, support or brace designed to support a patient in carrying the loads applied onto them by walking, running, manipulating objects and/or similar activities and/or by repositioning a limb or forcing them to move a certain way. They can also spread the pressure between the body and the shoe/ground/prosthetic over a larger surface area and provide cushioning to the loaded areas.
A prosthetic device is an artificial extension of the human body or a replacement of a lost body part, e.g. to replace a lost limb or any other body part. A prosthetic limb—upper or lower extremity—usually consists of a prosthetic socket which conforms to the residual limb, the artificial limb, such as a hand or leg and some means of attaching the limb to the socket.
Currently the design and manufacture of customized orthoses and prosthetic sockets is a multi-stage and labour intensive process with significant elements of clinical judgement, manufacturing craftsmanship and trial-and-error experimentation. Only a few standardized procedures exist in their design and manufacturing. This can lead to variation in the final product. The lengthy manufacturing process can also delay treatment.
Traditionally the orthoses and prosthetic manufacturing processes are very similar. Initially, a plaster cast of the relevant parts of the limb or residual limb is taken; this is then worked into a positive of the limb/residual limb, where certain interventions are applied by the craftsman manually. The modified positive is then vacuum formed or laminated using thermo-formable plastic. This device is then further modified, finished and fitted to the patient. Further manual modifications may be necessary, especially with prosthetic sockets, or when adding hinges to orthoses. Adding cushioning materials is also one step in the finishing procedure.
This process is completely manual, requiring considerable experience and skill. Each device is also unique, as the work stages are done slightly differently each time. Also, if several persons are working on the same device, each person has a different idea what is required.
In U.S. Pat. No. 6,968,246, a computer assisted system is described to address these issues. In the computer assisted approach, the technician manufacturing the orthoses or prosthesis can input the shape of the limb/residual limb in question into a computer system with the aid of a mechanical or a magnetic digitizer or a 3D laser scanner. This shape is then used to design an orthoses or prosthesis in specialist computer software that decreases the overall volume of the device by certain amounts. A pattern matching this shape can then be manufactured by using a 3D carver and vacuum molded or laminated as in the traditional process.
It is also known from the prior art, as described in the article in Volume 55(2) (2008) of the IEEE Transactions on Biomedical Engineering to Faustini entitled “Manufacture of passive dynamic ankle-foot orthoses using selective laser sintering.”, that customized orthotic or prosthetic devices may be manufactured using Selective Laser Sintering (SLS), a Rapid Prototyping and Manufacturing (RP&M) technique, where RP&M can be defined as a group of techniques used to quickly fabricate a scale model of an object typically using 3-D computer aided design (CAD) data of the object.
Cushioning is applied to these devices by using different materials attached on the main body of the device. The properties of the cushioning (e.g. varying from soft to hard) can be adjusted only by changing the material or the thickness of the cushioning element, which usually changes the shape of the surface. The cushioning material and thickness is typically homogeneous over the pressure carrying area. Local modifications, like local cushions such as metatarsal pads or bars, cutouts for the plantar fascia, etc. can be made manually by cutting out material or adding more of the same or a different material on top of the existing one to treat certain conditions. The purpose of cushioning is to absorb the forces placed on it through compression or elastic or plastic deformation of the cushioning material so that the user of the device with the cushioning will not have to absorb as much of the forces.
However, the need for time-consuming manual tasks makes the overall process slow and specialist equipment and supplies are needed. If the design is incorrect, the whole process has to be restarted. Moreover, the manual process of locating added cushioning features may result in problems with quality and consistency as every craftsman works slightly differently and creates different orthoses. The computer assisted process may alleviate some of these issues related in creating the positive and making the interventions to it, but adds more process steps in the orthoses creation chain and adds extra investment in training, equipment, milling materials which also create a lot of waste—without solving the problems with traditional manufacturing completely. The lamination/vacuum forming will still have to be done manually, as will the addition of features such as cushioning, hinges, cutouts, etc.
Patent application WO 97/03626 describes a modular interface connector for a prosthetic limb. The modular interface connector includes an interface cushion having a feathered periphery of tapered blades, which conforms to the inner surface of the socket of the residual limb.
The paper by Bill Rogers and others, “Case Report: Variably Compliant Transtibial Prosthetic Socket Fabricated Using Solid Freeform Fabrication”, Journal of Prosthetics and Orthothotics, 2008; 20:1-7, describes sockets fabricated using selective laser sintering, wherein compliance is provided by a diaphragm spring that is integrated into the socket wall.
In the article “Design and freeform fabrication of compliant cellular materials with graded stiffness” from the Solid Freeform Fabrication Symposium (Gupta, G., et al.), layer manufactured cushioning structures for prosthetic applications are described as solid base material arranged in cellular topologies that permit high levels of elastic deformation. The structures presented in this article may solve some of the problems found in prior art, but they do not offer all the advantages of the present invention.